21011959 has 2 divisors, whose sum is σ = 21011960. Its totient is φ = 21011958.

The previous prime is 21011957. The next prime is 21011981. The reversal of 21011959 is 95911012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21011959 - 2¹ = 21011957 is a prime.

Together with 21011957, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505979 + 10505980.

It is an arithmetic number, because the mean of its divisors is an integer number (10505980).

Almost surely, 2^21011959 is an apocalyptic number.

21011959 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011959 is an equidigital number, since it uses as much as digits as its factorization.

21011959 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 810, while the sum is 28.

The square root of 21011959 is about 4583.8803431154. The cubic root of 21011959 is about 275.9447790875.

The spelling of 21011959 in words is "twenty-one million, eleven thousand, nine hundred fifty-nine".